Question

How many of windmills are there?

(a) 2

(b) 3

(c) 4

(d) 5

This question was posed to me in unit test.

This question is from Wind Turbine Operation topic in portion Wind Energy of Energy Engineering

Answer 1

Right answer is (a) 2

To elaborate: There are two classes of windmill, horizontal axis and vertical axis. The vertical axis design was popular during the early development of the windmill. However, its inefficiency of operation let to the development of numerous horizontal axis designs.